The present invention relates to an arrangement for function checking of temperature sensors, which are used for maintaining a required temperature, within relatively close tolerances, in refrigeration vehicles and storage facilities. The temperature sensor includes a measuring element formed as a temperature-dependant variable resistor, and an electronic circuit for signal processional and frequency conversion.
It is known that economic as well as health considerations require that the temperature of refrigerated and freezed food products should be kept within relatively close tolerances along the distribution chain of the products from producers to consumers. For a responsible transportation contractor and a storage facility manager it is important to be able to document the compliance with the refrigeration requirements and, in case of a damage, to be able to furnish the insurer with a record showing that there was no absence of due care or willful disregard in maintaining necessary temperatures of the transporting stuff and/or there was no improper handling of the refrigeration equipment.
This means that it is necessary not only to be able to measure the storage, in particular, transportation temperature, but also to be able to continuously record them, with a plausibility of the recording being able to be confirmed by a neutral authority, e.g., Bureau of Standards. In other words, the temperature recording devices need be equipped with means capable to register functioning errors by random or automatic regular testing or to confirm proper functioning of the refrigeration equipment. In the later case, it should be able to produce a record indicating that no error or changes have taken place, but that rather, in case of damage, the refrigeration equipment was not adjusted to the required refrigerating temperature, which might have been made deliberately in order to save fuel. The simple way to effect such function checking is to check a temperature sensor of a temperature recording system which may include a temperature sensor, a recording device, an indication device and/or an output device. Generally, the temperature sensors, which register the temperature, e.g., in different areas of a refrigerator vehicle, are the critical elements of the system. The arrangement of the temperature sensors in locations, which are often not easily accessible and are obstructed by the product, and the necessity to hermetically seal the inputs and outputs of the temperature sensors, require a remote inquiry such that it would permit to effect checking of temperature sensor with a control device of a recording apparatus of a respective temperature recording system.
Accordingly, the object of the invention is to provide an arrangement which will permit a reliable remote function checking of a temperature sensor with minimum additional costs.